How do barnacles cement themselves to rocks?

Barnacles start life as larvae or ‘cyprids’ that swim around freely in the water. These cyprids must attach themselves to a hard substrate in order to complete the transition to adult life. When the cyprid finds an appropriate hard substrate to settle on it starts to attach itself using a ‘cement’.

A cyprid larvaIllustration: Jo Taylor / Source: Museum Victoria

The cement is released through the tips of the antennules (the first of two pairs of antennae). The cement is produced in glands at the base of the antennules, passes through ducts running up the centre of the antennule, and is released through the tip. The glands are regenerated and remain active throughout life. As the barnacle grows, the cement glands increase in size and become more complex. The broad base of the barnacles (where they are attached to the rock or substrate) continually develop secondary cement pores close to the growing margin, from which concentric rings of cement are released. The cement, which provides strong adhesion, is released as a clear liquid that hardens into an opaque, rubbery solid. It is composed of ‘quinone-tanned proteins’.

So a barnacle larva finds a nice-looking place to call its home, lands head-first and releases cement out of its antennules. It then spends its life stuck to the ground, flapping its legs about in a ‘hand-stand’ position!

Rocks are not the only places where barnacles settle. They also end up on wharf pilings and on the underside of boats. Many barnacles on a boat’s hull will slow it down and add considerably to the fuel bill because of the drag. Nautical engineers and chemists have developed anti-fouling paints that deter barnacle cyprids from settling. The poisonous chemicals in these paints, copper or tributyl-tin (TBT), leach into the water and do more than kill the barnacles – they are toxic to many other marine animals, and the use of TBT has been banned for small boats in harbours in many countries.

Comments (26)

hi i was just wondering about this rock what i found 3 days ago. 2 day later these people came to my school to talk to the calss about rocks so i asked them about it and they said it must be peace of plastic or pumus rock because the said pumum rock is the only rock in the world that floats in water and was pritty shocked because the rock that i found floated to.

Hi Tim! Thanks for your interesting enquiry, which we referred to our Principal Curator, Marine Biology. There are no studies to his knowledge about application of barnacle glue but he did think it sounded like a very good research project for someone!

Hi Matt, for further information about barnacles, you should look at the link to the right under related resources. You could also purchase the new book on Barnacles published by Museum Victoria. The Marine Education Society of Australia Life on Australian Shores website also has a good section on barnacles.

The following information is taken from 'Barnacles' by Gary C.B. Poore and Anna Syme;

Most common barnacles are hermaphrodites, having both male and female reproductive systems. A barnacle will therefore fertilise a neighbour and in turn be fertilised by a neighbour...Being unable to move as an adult adds extra importance in the larva’s ability to settle onto a surface close to other barnacles of the same species in order to be able to breed. This immobility helps explain why all barnacles live in colonies of numerous individuals often touching each other.

.....the (larva) chooses a place to settle, such as a rocky shore. The (larva) not only detects chemicals emitted from adults of its own species, it responds to signals from the shore itself – such as tidal level, wave exposure and roughness – which ensures that it locates a suitable place for the adult to live. ...Barnacles may live for up to ten years.

Hi Ron,Because of the way barnacles grow and attach to substrates they can foul steel structures. This is called 'calcareous (hard) fouling'. The process of removing this can cause damage to painted surfaces and subsequent damage to the steel by salt-water corrosion.

Thanks for your question about barnacles – perhaps you could look at the reference mentioned above on page 9 for the first part of your question. Barnacles have many receptors including eyes and are aware of their environments – such environmental factors as light and the chemical nature of the water surrounding them, and also the presence of other barnacles, are clearly the basis of their responses and reactions. They have a quite complex nervous system.

So far as removal of metabolic waste is concerned you might like to look at An introduction to the biology of British littoral barnacles See the section on “Excretion” on pages 11-12. Apparently there are glands on either side of the foregut and the main excretory product is ammonia. This paper also has detail of the nervous system of barnacles too.

With the exception of their limbs, which move in order to assist in their feeding, barnacles are unable to move in a locomotory sense as adults, so once a barnacle chooses a place to settle, it attaches itself permanently.

In the information above there is a sketch of a larva, which is the mobile stage of their development - barnacles start life as larvae or ‘cyprids’ that swim around freely in the water, as also stated above.

Student
23 January, 2013 05:50

Do you think there is any relationship between surface roughness and choice of attachment site? Is there any preference for their attachment sites? Thanks!

Discovery Centre
28 January, 2013 11:19

Hi Jo,

For further information about barnacles, you should look at the link to the The Marine Education Society of Australia Life on Australian Shores website which has a good section on barnacles and their behaviour.

Thanks for the awesome information.
I'm doing a report on the Barnacle for my Year 11 Biology. I was wonder what was the "cement" is? I can't seem to find any other information on the cement.
Thanks you !

I have an ancient "Mediterranean Pot" that is covered with barnacles inside and out. Said to be from a shipwreck, there is little to identify the pot. Some of the barnacles have come off and there is no paint below. Could the barnacles attachment disolve any paint if it was there?

hi i am doing a report for my biology class and i would like to know how the the Chamaesipho columna Barnacle digest its food and what enzymes and hormones help assist the process of digestion also how does it reproduce? i cant seem to find any helpful information